平板液相横流中气体射流的多尺度旋涡结构分析

Multi-Scale Vortex Structure Analysis of Gas Jets in Liquid-Phase Crossflow near the Flat Wall

为了研究平板液相横流中气体射流形态非稳态演化及流场中旋涡结构的多尺度演化过程,基于两步投影法和VOF界面捕捉方法,结合高分辨率网格策略,建立了平板液相横流中气体射流的高精度数值模拟方法.研究结果表明:平板液相横流中气体射流的演化过程可以分为射流气泡初步形成、射流气液界面失稳和射流气泡充分发展3个典型阶段.在Kelvin-Helmholtz不稳定性的诱导下,气液界面发生形变并逐渐失稳产生破碎,导致射流形态由大尺度连续气泡逐渐转变为小尺度离散气泡.平板液相横流中气体射流的涡系结构主要包括射流内部和气液界面的反旋转涡对、近壁面和射流界面的剪切层涡以及通气孔前缘的马蹄涡.各种旋涡结构在流场不同发展阶段扮演不同的作用,并相互作用导致了射流气泡演变过程的复杂多尺度流动.

In order to study the unsteady evolution of the gas jet morphology and the multi-scale evolution of the vortex structure in the flow field,a high-precision numerical simulation method for gas jets in liquid-phase horizontal flow was established based on the two-step projection method and the VOF interface capture method,combining with the high-resolution mesh strategy.The results show that the evolution of the gas jet in the horizontal flow can be divided into three typical stages,including the initial formation of the jet bubble,the instability in the gas-liquid interface and the full development of the jet bubble.Induced by the Kelvin-Helmholtz instability,the gas-liquid interface deforms and gradually becomes unstable,resulting in the fracture of the jet flow,which gradually changes from large-scale continuous bubbles to small-scale discrete bubbles.The vortex system structure of the gas jet mainly consists of counter-rotating vortex pairs inside the jet and at the gas-liquid interface,shear-layer vortices near the wall and at the gas-liquid interface,and horseshoe vortices at the leading edge of the vent.Various vortex structures play different roles in different development stages of the flow field,and their interactions lead to complex multi-scale flows during the evolution of jet bubbles.